Manager Ronny Deila aims to make at least one more signing before Celtic's Champions League play-off.
However, the Norwegian has been frustrated in his pursuit of fresh faces, revealing that the club had missed out on Haiti star Jeff Louis.
"I really hope we can get a player to make a difference in the games against Maribor," Deila said, looking ahead to the first leg in Slovenia on 20 August.
"It's a hard market but if the right player is there, money is available."
He had previously brought in forward Jo Inge Berget from Cardiff, again on loan, and out-of-contract goalkeeper Craig Gordon.
The Scottish champions sold keeper Fraser Forster to Southampton at the weekend and Deila would like to spend some of the £10m fee.
He said Nancy had accepted a bid for attacking midfielder Louis but the player had instead opted to join Standard Liege in Belgium.
"I have money to spend and that is the most important thing," Deila added.
"But if we buy a player for £10m what do you think the salary of that player will be? It will be five or six times more than you get at Celtic.
"If we pay that, what will happen to the other players? You have to see the big picture. It is not about the fee, it is about salaries.
"The money from television in the English Premier League is huge. Celtic is unbelievably huge but the money is not so huge.
"It has to be driven in a good way and Celtic have done that for many years and will continue to do so."
Deila did not rule out any more summer sales but insisted defender Virgil van Dijk wants to stay at Celtic Park and stressed that he was pleased with the quality of players he has inherited.
"There is still a long time to go in the transfer market," he said.
"In my head I know what I want. We'll see if it's possible. If I get it, I'll be happy and I think the fans will be too.
"But it's important to keep consistency and do things slowly. You can't do it all in one window. It's important not to lose your head."